Despite it's size and focus at the consumer market, Facebook is very much a company driven by software and developers. This shows in their efforts of creating (sometimes rather unique) solutions to their own internal problems and then sharing those as Open Source. Just like the Symfony community, Facebook invests in Developer Experience by providing development tooling for these solutions.

Java Virtual Machine as a platform seems to have gone through a renaissance, not exactly the same as PHP, but similar. Somehow languages ranging from Scala to Clojure to Ruby are raising the JVM fever. And this all makes sense.

Over the years there has been tremendous investment to JVM as a platform. The original JVM language, Java, might seem stale to some - but the shared runtime allows inheriting this heritage with new syntax and paradigms.

People love to pit two competing products together. Be it sports cars, cameras or software. Everyone likes to cheer for their personal preference. This is now happening with PHP 7, HHVM and others inspiring people to create pointless benchmarks.

Hack is a programming language for the HipHop Virtual Machine (HHVM), created by Facebook as a dialect of PHP. The language implementation is open source, licensed under the BSD License.

While it is close to PHP it is not that exactly and can move away from the realm altogether as it progresses. In modern web development you'll need an IDE to keep your project organized and help you perform routine tasks easily.